NIOSH recently conducted a health hazard evaluation regarding the potential risk of rhabdomyolysis and heat-related illness in cadets and instructors participating in firefighter training courses, which included outdoor physical training and live-fire suppression exercises in full protective gear. Rhabdomyolysis, the breakdown of muscle tissue, can be caused by overheating, overexertion, crush injury, and certain medications, supplements, or medical conditions. During NIOSH’s four-day visit in August 2012, agency staff provided a questionnaire to 32 participants regarding work and medical history and health symptoms, and measured the body temperature and heart rate of 22 participants. NIOSH staff also monitored fluid intake, analyzed blood markers for dehydration and muscle breakdown, and measured environmental conditions and body weight before and after each training day. The evaluation revealed one person with rhabdomyolysis. NIOSH also found that environmental conditions often exceeded heat stress limits, and at some point during training, many participants met the agency’s criteria for excessive heat strain. Sixteen participants experienced muscle breakdown, but did not require medical attention. In most participants, levels of markers for dehydration and muscle breakdown decreased from the beginning and end of each training day. This suggested the firefighters remained appropriately hydrated. NIOSH recommended the employer begin scheduling physically demanding activities during cooler parts of the day. In addition, NIOSH recommended employees learn more about the signs and symptoms of rhabdomyolysis and other heat-related illnesses, alert a supervisor immediately if the signs or symptoms occur, and talk to their healthcare provider about increased risk for rhabdomyolysis. View the .